Connecting rod



H. C. HILL.

CONNECTING ROD March 14, 1939.

2 Sheets-Sheet 1 Filed May 2'7, 195'? 1m 'ENTOR. HENRY (L/ ON [LL March14, 1939. H. c. HILL CONNECTING ROD 2 Sheets-Sheet 2 Filed May 27, 1937mwkw INVENTOR W m w m w M N M N J a m N W Patented Mar. 14, 1939 UNITEDSTATES CONNECTING ROD Henry 0. Hill, Paterson, N. J assignor to WrightAeronautical Corporation, a corporation of New York Application May 27,1937, Serial No. 144,985

5 Claims.

This invention relates to improvements in connecting rod systems forradial cylinder engines.

An object of the invention is to provide a rod system which more closelyapproaches a so-called "true motion rod system, than may be approachedby the conventional master rod and articulated rod arrangement.

A further object of the invention is to provide a rod system wherein therod motion and piston travel for pistons connected to the rods is thesame for all rods and pistons of the assembly.

A further object-is to provide a system wherein each connecting rod, atcertain intervals during the rotation of the crankpin, functions as amaster connecting rod.

Still another object is to provide a rod system wherein all of theconnecting rods are pivoted to and osciliatable with respect to abearing member embracing the crankpin, and to so organize the systemthat said bearing member is constrained to an orbital path with thecrankpin with substantially no rotation.

Still another object is to provide a rod system wherein a bearingmember, to which a plurality of connecting rods are articulated, isendowed with properties of damping, in some degree, torque reaction ofthe engine.

A great number of connecting rod systems for radial engines have beenproposed, the principal system now in use comprising a master rodembracing the crankpin of a crankshaft, said rod having articulatedthereto a plurality of subsidiary rods. In such a system, the master rodhas true motion, but the subsidiary rods, due to their angulation withrespect to the master rod, do not have true motion, and the pistonscarried on the several auxiliary rods will have errors in displacementin accordance with the angular position of the crankshaft, making itimpossible to completely balance the reciprocating parts withcounterweights. Furthermore, valve and spark timing errors areintroduced by the errors in piston positions. These errors result inroughness in engine operation and loss of optimum performance whichbecomes particularly objectionable in large displacement, high poweroutput engines. Many attempts have been made to alleviate thisdifiiculty, some of which comprise the use of slipper type rods whereall of the rods will have true motion and will move about the crankpincenter. Such systems, particularly when the number of engine cylindersis seven or nine, restrict the bearing area of the rods and involveconsiderable difflculty in fabrication. Still another system has beenproposed wherein all connecting rods are articulated to a spool memberembracing the crankpin, and means are provided to prevent rotation ofthe spool so that each connecting rod will have the same path of motionduring rotation of the crankpin. It is with the latter class of rodsystems that this invention is more or less associated, but the addedcomplication of mechanism necessary to hold the spool from rotation iswholly eliminated.

The details of the invention may be better understood by a reading ofthe annexed specification in connection with the drawings, in whichsimilar numbers indicate similar parts, and in which: a

Fig. 1 is an end view of a nine cylinder radial rod system applied tothe crankpin of a shaft;

- Fig. 2 is a side elevation of a crankshaft showing a portion of therod system in section;

Fig. 3 is a section on the line 3-3 of Fig. 2;

Fig. 4 is a graph showing clearances with respect to crank angle; and IFig. 5 is a fragmentary elevation of an alternative form of abutmentdevice.

Referring to the drawings, the letters a to i, inclusive, designate theaxes of the cylinders of a nine cylinder radial engine, all of theseaxes intersecting at the axis of a crankshaft member l0, provided with acrankcheek I I and a crankpin I2. A crankpin bearing member I3 is inbearing engagement with the crankpin l2 through a bushing I4, andcomprises a crankpin embracing portion l5 and flanges l 6 and I1extending therefrom. These flanges are pierced for the reception of pinsI8 upon which are journaled a plurality of identical rods IS, the rodsbeing designated by letters corresponding to their cylinders, the pinsit permitting of free oscillation of the several rods with respect tothe bearing member I3 and with respect to each other.

In order to define the limits of oscillation of the rods with respect tothe member l3, each rod is provided, outward of the pin [8, with pairsof oppositely facing abutments 20 and 2| which are adapted to cooperatewith fingers 22 extending radially outward from the flanges l6 and ll ofthe member l3, each of these fingers having an abutment 23 which may beengaged by the abutment 20, and having .an abutment 24 which may beengaged by the abutment 2|. The several abutments and fingers 20-24 aredesignated by letters corresponding to the rods and cylinders with whichthey are related.

The included angle between the abutments 23 and 24 is manufactured sothat, when one rod cylinder, the abutments on the two rods in thecylinders whose axes are nearest to 90 from the aforementioned cylinder,are each substantially in contact with their respective fingers 22 onthe bearing member. This is indicated in Fig. 1, where the rod I97. forcylinder 7:. is shown with its abutment 2 Ih in contact with the fingerabutment 24h, and the rod for cylinder is shown with its abutment 200 incontact with the finger abutment 230, where the rod in cylinder a is atits top center position.

Assuming the rod 19a to be in top dead center position as shown, theabutments 2471. and 230 which coact with the rods I972. and 19erespecifcounter-clockwise rotation is assumed in Fig. 1,

the rod I90 has gone past, its position of maximum angularity by and therod i972. is

ahead of its position of maximum angularity by 10. However, as thecrankpin l2 moves through its next 10 from the position shown, theabutments 20c and 230 will separate to provide clearance at a greaterrate than the abutments 2m and 24h tend to reduce the clearance, sothat, at the 10 point, there will be a slight looseness of the memberI3, permitting free oscillation thereof between abutments 23c and 2471.except for the fact that the forces imposed on the system will tend tokeep the abutments 2Ih-24h in contact, The member l3 will be turnedclockwise slightly from its true motion orbit by the approach of the rodl9h to its maximum angularity position. After the 10 point, to the 20point, the abutments 206-2311 will begin to approach each other to closeup their clearance while the memberlii moves counter-clockwise due toits continued abutment with the rod lilh. The complete closing willoccur at 20 past center, whereupon the rods l9d and l9h hold the memberl3 in neutral position. Thereafter, for the next 10, the abutments ofrods i9d and 99h spread to increase the clearance to allow maximumclearance at the 30 point, and during the next 10? of crank rotation,the rods IM and 19d close in to hold the member l3 from oscillation atthe 40 point when the rod I971. is in its top dead center position.

Fig. 4 of the drawings graphically illustrates several cycles of bearingmember freedom and constraint, the areas which are hatched being crankangle stations where clearance occurs, and the intermediate curve ofsine-wave form representing the angular excursions of the bearing. Thesuccessive stages of activity of sets of abutments 20-23 and 21-24 areindicated with respect to those rods l9a to i which are currently activeas master rods.

The successive functioning of the several abutments imparts to themember l3 a slight angular oscillation or vibration, the magnitude ofwhich is very small. For instance, the total normal angular excursion ofthe member 13 is only .46 and the maximum clearance possible to permitfreedom of the member i3 is only .020" in a practical design for a ninecylinder rod system.

certain bending moments will be imposed in that rod by virtue of thetorsional moment induced in the member i3 by power impulses of that orthose rods which are driving the crankpin. These bending moments,however, are of a sufficiently small magnitude so that the severalconnecting rods may be made in proportions which are useful andpractical. One advantage flows from the use of all of the rods of thesystem as master rods at intervals in that piston side pressuresresulting from. bending moments on the rods and from other causes, aredistributed to all cylinders rather than to only one cylinder as obtainsin the case of the master connecting rod construction.

The angular displacement of the member l3 from a true motion orbitalpath as the crankpin rotates, will have, practically, an infinitelysmall egiect in upsetting piston displacement relations ps.

Another characteristic of the system is that those rods which are actingasmaster rods at any one time are not subject to power impulses fromtheir respective cylinders-that is, those rods which are transmittingpower impulses from their respective pistons to the crankpin, aresubstantially free of any bending stresses at that instant. The rodswhich are acting as master rods will be stressed in bending without theadded stress due to power transmission from their respective pistons tothe crankpin.

It appears presently that a system of this kind would be most applicableto an engine having a large number of cylinders-if only three or fivecylinders were embodied in the engine, the free motion of the member 13might become excessive. But with engines having seven, and moreparticularly nine cylinders, the free action of the member I3 is of sucha small order asto make the system distinctly practical. However, if thebearing member is constrained to the sine wave orbit by forces ofoperation, the system may have equal utility in engines of other numbersof cylinders.

In the description above, it has been indicated that the angles ofabutments 23 and 24 are such as to just permit of abutment of theconnecting rods at certain times, without clearance at that time orwithout a jamming effect. However, in certain environments, it may beconsidered advisable to allow for clearance instead of positive contactof both rods with the bearing member, as indicated for rods I and l9h inFig. 1. One consideration in this respect is the removal of the naturalvibration frequency of the member l3 and associated parts from possiblesynchronism with the exciting impulses. It is also feasible to arrangethe abutments 23 and 24 with negative clearance, whereby jamming wouldoccur when said abutments engage their respective rods. Such jammingwould cause deflections in the fingers 22 and in the connecting rods,

which can be designed with sufficient flexibility flexible, the total orpartial jamming of the rods and bearing member, by omitting theclearance apparently needed by the geometry of the system, would imposeno undue hardship nor prevent proper functioning of the enginecomponents.

Fig. 5 shows an alternative form of resilient finger 22', wherein thefinger is slotted or bifurcated as at 25 whereby the abutments 23' and24 are mounted, in eilect, on stiff springs. Such an arrangement or anyequivalent one,

would allow of positive contact of abutments 20-23 and 2I-24 withoutrelative clearance, and the slot 25 would be made of a width equivalentto the maximum geometrical clearance indicated in Fig. 4. Thereby, bothelements of the bifurcated finger 22' would function as a relativelypositive stop when the slot 25 is closed by deflection of one of thebifurcations.

In Fig. 4, the curve A represents the effective angular excursions ofthe member l3 as calculated for a system operating at a speed of about2300 R. P. M., taking into consideration the masses, forces andmovements of all parts of the system. It is apparent that the operatingvibration amplitude is extremely small so that no harmful efiects wouldbe produced in the engine.

The efiect of engine explosions on this sine wave of angular excursionsis calculated. to be a modification of the wave form equivalent tomathematical additions of the principal sinusoidal component ofexplosion torque variation, and, in considerationof a certain amount 01flexibility in the rods and associated parts, a damping eifect on torquevibration transmitted to the engine mounting structure, is expected withproperly proportioned parts.

In Figs. 1 and 2 of the drawings, means 30 are shown to retain the pinl8 in the member 13, and to hold them from rotation, such meanscomprising a strip 3| overlying the end of the pin l8, having a lip 32engaging part of the member l3 to hold it from rotation, and a nut lock33 engaging the strip 3| and having a tab 34 for locking engagement withthe head 35 of a screw 36 screwed into a suitable bore in the pin I8.'I'he crankarm l I is shown as being provided with a conventionalcounterweight 38. The system of abutments (20, 23, 2|, 24) shown in thedrawings illustrates only one of a number of practical forms of devicesfor limiting oscillation of the rods with respect to the bearing member,and it is not intended that the specific form of abutment means shown beconstrued as a limitation of the scope of the invention.

While I have described my invention in detail in its present preferredembodiment, it will be obvious to those skilled in the art, afterunderstanding my invention, that various changes and modifications maybe made therein without departing from the spirit or scope thereof. Iaim in the appended claims to cover all such modifications and changes.

I claim as my invention:

1. In a radial cylinder engine having a crankpin, a bearing hub on saidcrankpin, a. plurality of similar connecting rods for the cylindersarticulated to said hub, and resilient abutments on said hub engageablesequentially by said rods and having negative clearance relative tothose rods with which they engage, the abutments being so closely spacedrelative to said rods as to enforce a series of advancing and retreatingmovements of the hub due to engagement of the rods with said abutments.

2. In a radial cylinder engine having a crankpin and an odd number ofcylinders, a bearing hub on the crankpin, connecting rods articulated tosaid hub and engaging said cylinders, abutments on said hub so spaced asto positively engage both of those connecting rods of cylinders whichare nearest to 90 away from that cylinder whose connecting rod is at topcenter position, and resilient means for cushioning the engagement ofthe rods with said abutments.

3. In a radial cylinder engine having a crankpin, a hub borne on thecrankpin comprising axially spaced flanges integral with a bearing, aplurality of connecting rods having their inner ends disposed betweenand pivoted to said flanges, fingers extending substantially radiallyoutward from said flanges between respective rod pivots, and fingersextending from each rod in a direction substantially parallel to thecrankpin axis for abutting engagement with said flange fingers and soproportioned as to sequentially engage said flange fingers in abuttingrelationship.

4. In a radial cylinder engine having a crankpin, a hub borne on thecrankpin comprising axially spaced flanges integral with a bearing, aplurality of connecting rods having their inner ends disposed betweenand pivoted to said flanges, fingers extending substantially radiallyoutward from said flanges between respective rod pivots, and fingersextending from each rod in a direction substantially parallel to thecrankpin axis for abutting engagement with said flange fingers and soproportioned as to sequentially engage said flange fingers in abuttingrelationship, the flange and rod fingers having resilient reaction withrespect to one another in a circumferential direction to cushion theabutments of the rod fingers with the flange fingers.

5. In a connecting rod system for a radial cylinder internal combustionengine including a crankshaft having a crankpin, a bearing on thecrankpin carrying circumierentially disposed knuckle pins, a connectingrod articulated on each knuckle pin, the several rods being adapted forrelative angulation during crankpin rotation, abutments formed on saidrods, and abutments formed on said bearing, between the knuckle pins,with which said rod abutments are engageable, the included angle betweenany substantially diametrically opposed pair of oppositely facingbearing abutments being greater than the minimum included angle betweenthe rod abutments of corresponding rods to enforce pressure contact ofthe rod abutments with the bearing abutments when respective rods are inposition for a minimum included angle, and resilient means incorporatedin the abutmentsv to absorb the enforced pressure contact to theelimination of fracture of the associated parts.

HENRY GRILL.

